This invention pertains to a can handling system for handling case, such as beverage cans, which have printed material and varnish applied thereto and which must be moved through an oven for baking of the applied material without contact between the cans.
More particularly, the invention pertains to a can handling system wherein individual cans are mounted upon individual free-standing can carriers and the can carriers are conveyed to and through an oven, with each can mounted in a manner to prevent contact with a can on an adjacent can carrier.
Many cans, particularly beverage cans, are printed before filling by movement through a high speed printing machine that can handle several hundred cans per minute. It is conventional to associate a pin chain conveyor with the printer or coater for conveying the printed cans from the printer and directing festooned lengths of the pin chain conveyor through an oven for drying or baking the printed material as well as varnish that has been applied to the can bottom. In order to handle the production rate of the printer, it is necessary to have a large oven and a substantial length of pin chain conveyor in order to provide the festoons which results in substantial cost. There is a drive relation between the pin chain conveyor and the printer or coater and, as a result, frequent stoppages of the structure, due to malfunctions in the printing machine, has resulted in the stoppage of the pin chain conveyor, including the festooned lengths in the oven. This causes overheating and improper treatment of some cans within the oven. Efforts to avoid this have necessitated "quick cool" and "quick heat-up" features within the oven which are costly and not fully reliable in operation.
One example of a system attempting to avoid the use of a pin chain conveyor with an oven is shown in Schregenberger U.S. Pat. No. 3,958,683. The patent discloses a conveyor system wherein cans are handled by several different vacuum units for removal from a pin chain conveyor and placement in rows for travel through an oven. The conveyor handling structure disclosed in this patent embodies many complex mechanisms and requires repeated engagement and release of cans with there being the possibility of a can not remaining in erect position.
A commercially available system utilizes an oven wherein the cans pass through the oven single file at a constant speed and prior to entry into the oven are removed from the pin chain conveyor. This system avoids the problems effected by stoppage of the pin chain. However, problems are encountered in this system with the conveyor and the short time cycle for baking of a can when the cans have to run up to speeds of 800 to 1,000 cans per minute through an oven of a reasonable length.